Metal-mold.



I 74 1 Q g F. A. P ARKHURST.

METAL MOLD- 4 APPLICATION FILED OCT- 1. l ll' 4 1,296,596. Patented Mar. 4.1919.

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. Patented Mar. 4,1919.

31402 n lioz F. A. PARKHURST.

METAL MOLD. APPLICATION FILED 0011.191].

Patented Mar. 4, 1919.

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METAL MOLD. 7 APPLICATION FILED OCT- l. I911.

- Patented Mar 4.1.919.

' APPLICATION FILED OCT-1.1917

F. A. PARKHURST.

METAL MOLD.

J vT 5 746 a 4 --J I-. 4 1 7 1' 26 HI ll 74d I lxwiwwo Patented Mar. 4,1919.

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314412 ntoz F. A. PARKHURSL- METAL MOLD.

ABBLICATIQN FILED OCT-1. 1911. 1;296,596. Patented Mar. 4.1919.

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UNITED STATES PATENT orinon.

FEEDER-IO A. PARKHURST, OF GLEVELAN D, OHIO, ASSIGNOR TO THE ALUMINUM" CASTINGS COMPANY, OF' CLEVELAND, OHIO, A CORPORATION OF OHIO.

METAL-MOLD.

Specification of Letters Patent.

Patented Mar. 4, 1919.

Application filed October 1, 1917. Serial No. 194,189.

To all whom it may concern:

Be it known that I, Fnnonnro A. PARK- HURST, a citizen of the United States, residshaped castings such as skirted pistons for internal combustion engines.

comparatively recently pistons" of this kind made of aluminum alloys have come into extensive use, their light weight giving them a marked advantage over the heavier iron pistons. Of these light weight pistons those cast in permanent metal molds have been most successful because of their internal structural characteristics which give the v castings great strength and superior machining and bearing qualities. r

' However, the internal projections characteristic of internal combustion engine pistons of the skirted type have given'rise to difliculties which have been very hard to overcome in the production of permanent mold cast1ngs."As is well known to those familiar with internal combustion", engine practice in the less recent past, the pistons were provided with internal bosses which form the bearing support of the piston pin,

usually with aninternal rib or ribs which extend from the piston head and the side walls and serve both to strengthen the piston ,and facilitate the dissipation of heat from the piston head, and also with an internal annular, circumferenti'ally extending flange or thickening of the side wall at or near the bottom or open end of the piston, sueh flange grooves. r

Up to the time of my invention 'considerable progress had' been made in the development of permanent molds for the production of piston castings, and permanent metal molds having sectional cores have been produced in which it was possible to cast pistons. with internalpin bosses and head ribs, but. it had'been impossible to produce pistons of the character in question with an internal circumferential flange at or near the bottom of the piston skirt because of the difficulties incident to supporting the core parts accurately and rigidly and to providing clearance necessary for the withdrawal of the core parts.

Accordingly, upto the time of my invention, one of three alternative courses had been followed in the production of these permanent mold pistons, namely, (1) the side walls of the pistons were thickened throughout their length so as to give the desired sti-fl'ness and strength at the lower end of the skirt, but at the expense of a very substantial increase in the weight of the piston; or (2) the side walls of the piston were relievedby forming an external circumferential depression around the middle part of the skirt thus leaving the wall adjacent the head of adequate thickness for the piston ring grooves, and the wall adjacent the .bottom'of the skirt of adequate thickness to afford strength and, in some cases, provide a groove for/a wiping ring',.while unnecessary metal in the intermediate part of the wall-Was eliminated and a minimum weight attained; or *(3) a compromise was effected with respect to the factors of weight on the one hand and strength and stiflness on the other by making the side walls moderately heavy throughout so that the weight.

was not increased as much as in the first case and suflicient strength and stiffness was provided to prevent failure of the pistons though not enough to insure entirely satisfactory operation.

Obviously neither of these three forms of construction is satisfactoi vfor'thefirst sacrrifices lightness, which is the prime result sought in the use of the light metals, the second course, that is relieving the exterior of the piston walls, rolbs the piston of a large part of its bearing surface which is ion needed to withstand the-lateral component of the piston rod thrust, while the third course is obviously unsatisfactoryw ith respect to the sacrifice of lightness and the lack-of adequate strength.

The'o'bject of my invention is the provision of a permanent mold for the casting v -of pistons of the character referred to in which the foregoing difliculties are overcome and by means of which it is possible to produce piston castings having a scientific disposition of the metal to secure a mini-' mum weight, a sulbstantially continuous external bearing surface, adequate internal ri-bs, if desired, for strengthening purposes and for cooling the head of the piston, and an internal circumferential reinforcement of -the lower wall of the piston skirt-to provide adequate strength and stiffness and to or morewiping rmgs. .15

also malge'possi'ble, if desired, the use of one The manner in which I attain the foregoing results will be clear from the following description, in connection with the accom .panying drawings, in which Iset forth for purposes of explanation and illustration a preferred embodiment of the invention.

In the drawings V Figure l'is a plan view of a piston mold 4 embodying my invention, parts ofthe mold J of Fig. 1;

sections on'the lines 5-5 and 66, respecing one of the middle core'sections removed 85 and the other middle core sections moved tively, of Fig. 4;

-- Fig. 7 is a view similar to Fig. 6' but showlaterally inward to illustrate the manner of freeing. the salmefor removal;

- Fig. 8 ,is,,another view similar to Fig 6 but showing all the middle core sections removed so as to afford clearance for the removal of thequarter sections of the core,

one of the latter being swung laterally into a position freeing it" for lengthwise movement;

Fig. 9 is a'detached perspective view\ of a the inserts, used for venting the upper end of the mold cavlty; v Fig. 10 is a fragmentary vertical section through the upper part of the mold body showing the venting inserts illustrated in Fig. 9 eperatively assembled;

Fig. 11 is an outside elevation of one of the palrs of quarter sections of the mold core- Y Fig. 12 is a central vertical section through the mold core; v

Fig. 13 is a bottom view of the core;

Flg. 14 1s a fragmentary vertical section similar to Fig. 3 but showing a modifiedform of construction;

Fig. 15 is a Fig. 16 is an outside elevation of one of the pairs of quarter sections of the core shown in Fig. 14;

bottom view of the core shown in Fig. 14;

' Fig. 17 is an inside elevation of the cor sections shown in Fig. 16.

In carrying out my invention the ma n part or body of the mold forming the outer Figs. 1 to 13, inclusive, of the drawings, the

body of the mold is shown as comprising a base 1 and complementary members 2 and 3 movable on the base toward and from each other. -These three main sections of' the mold body are preferably formed from cast iron.

Each of the complementary members 2 and 3 comprises an inner'side wall 4, end walls '5 and 6 and top and bottom walls 7 and 8, respectively. Each of these members is also preferably formed with a series of internal Webs or walls 9, 9, and 10 parallel to the -end walls 5, 6. The outer side of each of the complementary members is formed bv a plate 11 bolted to the casting.

, Handles12, 12 are secured to plates 11, 11

so that the side members of the mold can conveniently be moved to and from operative position on the base. v

. The inner side walls 4 of the complementary members of the mold body mutually engage when said members are moved together, as shown in Fig. 1. Each wall 4 is drical portion 4 and the lower parts ofthese semi-cylindrical walls 4 form the outer side wall of the mold cavity, the'bottom of said cavity being formed by the upper face of the base 1. The upper face of the base 1 is formed with a central depression 1 which provides for a work sp'pt on the'head of the piston casting. ii I 4 At 1 the basel is provided with a circular shoulder and the'bottom walls 8, 8' of the side members 2 and 3 ai'e recessed at 8 to receive the shoulder 1' whereby the mold members 2,3 are properly alined relatively 116 to each other and also centered on the base plate 1. Supplemental means for alining the side members of the mold may be employed if desired,such for example, as'pins 13 which extend upward from the base 1 to be-engaged by recesses4" formed in the walls 40f the side members of the mold.

Above the'mold cavity proper the semi- At 16 are devices for locking the mold members 2' and 3 together in operative posi- I y the inserts 14, (Figs. 4 and 5) The spaces at the two sides of e middle sections 17, 17 17 are occupie by two pairs of sections 17 17 d which, for the sake of convenience, I will call quarter sections.

The core surfaces below the inserts 14 form the inner side and bottom walls of the mold cavity proper, said core Surfaces being formed with various depressions to provide for the desired contour of the interior of the piston casting. As indicated in Figs. 11 and Y12 the quarter sections ofeach pair are shaped with the recess a to form the wrist pin bosses of the piston casting, onehalf of the recess being formed in each quarter section of the core. This construction permits these sections 17 17 fto be moved laterally apartand disengaged from the 'bosses of the casting. In the construction shown the adjacent faces of the core sections 17 are recessed at b, c to form strengthening ribs between the pin bosses and the side walls of the piston, and at their lower ends eachpair of quarter sections is recessed at d and the interlor middle sect1on 17 is recessed at e, sald recesses d, 6

providing for a strengthening and heat dissipating rib on the inner side of the piston head in a plane parallel to the axis of the pin bosses andin line with the ribs formed by the recesses 19, 0.-

. I At its lower ends the core is of reduced diameter at-17 to make the side wall of the piston casting adjacent the head of ample thickness to accommodate packing rings,

And between-the recesses a for the piston pin-bosses and the upper end of themold cavit the core is formed with a circumfer-' enti depression 7 to provide an internal flange 0n the skirted piston near the open end thereof for. the double purpose. of strengthening and stiffening the lowerend of the piston and providing space for a wiping ring.

sections be rigidly-and accurately sup orted in relation to ,each' other and in relation to the body of the mold and I have made provi- ..sion to this end. The dimensions, of the core sections are such that when assembled the core snugly fits the cylindrical wall formed .by the inserts 14 of the mold body. In addition the core sections 17, 17 are formed It is exceedinglyimportant that the core with outwardly turned flanges 18 which rest upon the top walls 7 of the mold body to limit the downward movement of said: core sections, and the sections 17 are provided with outwardly turned flanges 19 for a similar purpose. Also the interior core section 17 is formed with shoulders 20 which engage the upper ends of the sections 17" and 17. The section 17 b is also formed with flanges 21 which are adapted to be engaged by a tool to facilitate the loosening of the central section when the core is withdrawn from the mold. Y

To insure the accurate positioning of the core circumferentially, the middle section 17* is provided with a key 22 suitably secured as by screws 23, and this key engages a groove in the adjacent wall of themold body formed between the wear plates 24,-

24:, the walls 4 of the side members 2 and 3 of the mold, as well as the inserts 14, being cut away to receive said wear plates 24 which are secured in position by screws 25 (Figs. 4, 5 and 10). A further means of accurately and rigidly locating the core sections is provided in the form of a pin 26 which is mounted in the upper side wall of the core section 17 b so as to extend laterally into' engagement with a "corresponding groove in the adjacent face of the core section 17. The middle core sections 17, 17 are tapered on two sides toward their lower ends, the section 17 is similarly tapered on all four sides and the respective sections are,

nicely fitted on their abutting faces to each other and on their outer curvilinear faces to the mold walls 1; so that when the core is assembled in the mold body it is both accurately positioned and rigidly supported.

To facilitate the. handling of the core.

parts the middle sections 17*, 17, 17 are provided with handles 27, 28 and 29, respectively, and the quarter sections 17 am provided with handles 30. I For the purpose of coring. out the pin bosses of the piston casting, a vco re pin 31, preferably of steel,.is removably mounted in each of the mold sections 2 and 3 so as to proj ect into the pin boss cavity. A steel wearing sleeve 32 is preferably provided for each of .the' pins, the plnand the bore ofthe sleeve that its inner end engages the "metal of the quarter core sections as indicated in Fig. 3. The body of themold may be formed or provided with any suitable sort of gate for the introduction of the molten metal into the mold cavity; In theconstruction illustrated I employ a pouring gate 33 which communialining-recessesformed in the adjacent arts of the walls 4 of the mold members 2 and 3.

- To facilitate the escape of air and gases being v correspondingly tapered to insure a. snug fit and the'length of the pin being such I cates with the mold cavity from the top to the bottom thereof, the gate being formed by from the mold special venting means may be and preferably are provided. In the construction. shown the inserts 14 are formed with grooves 14 on their inner faces, with grooves 14 on their outer-faces and with grooves l t and 14 on their top and bottom faces, respectively. These grooves insure the escapeof air or gases which find their way to the top of the mold cavity. Also the-base 1 may be bored out centrally to receive a plug 34 which is provided with flats or grooves on its Outer surfaces which constitute passages for the escape of air or gases downward through the base.

.I have also-formed grooves 35 in one or both of the adjacent facesof each pair of quarter sections 17 as shown in Figs. 3 and 12. Then I preferably drill a passage 36 in one of each pair of the core sections 17 and insert in the lower part of said passage a grooved plug 37, thus providing one or more .mmute passages leading from the pin boss cavity upward to the top'of the core. Air. or gases rising in the rib recesses'd escape upward through the grooves 35, thence upward and around the 'core pins 31 and out through the passages 36.

It is usually desirable to provide for heating the bodyof the mold to maintain it at a suitable temperature and I have shown burners 38, 38 mounted on brackets 39, v39,

said burners being arranged so that their flames are directed through openings 11 in the plates 11 to heat the inner. walls of the m'oldmembers 2 and 3 and particularly the Walls 4: in which the gate 33 is formed, this arrangement insuring that the-metal in the gate shall remain molten longer than that in the mold cavity.

The walls of the mold, including core parts, which constitute the walls for the mold cavity are suitably coated or treated in any well known manner to reduce as much as possible agltation of the molten metal as it flows into contact therewith and to insure i proper setting of the metal within the cavity.

In the operation of the mold above described the members 2 and 3 are first moved together. into operative position on the base 1. Next the main core 17 .is introduced. The

pquarter sections 17- are first lowered into position in the mold cavity approximately in 1 the positions they should occupy; then the middle section 17 is inserted and, by reason of its interlocking engagement with the core body, serves to adjust the quarter sections circumferentially more exactly to their.

proper positions; then the middle section 17 is introduced, and lastly the interior middle section. 17 is inserted so as toaccurately position each and all of the core sections by reason of their mutual enga ement. The locking devices 16 are then riven tightly home so as to clamp the main core sections and render the whole structure Next the core pins 31 are inserted.

' The temperatures at which the various parts are maintained will depend largely. upon the nature of the metal or. alloy to be cast. But assuming that the burners 38 have been operated to heat the mold parts to the desired temperature, the mold. is now ready to receive the molten metal. Said metal is brought tothe mold in any suitable manner,

as by a ladle, and is 'pouredinto the inlet of the gate 33 through which it enters the mold cavity. I prefer to use a gate 33, suchity and also to materially reduce splashing of the "metal within the gate during pouring.

Splashing is further reduced by forming the gate wall as shown so that the metal flows smoothly along it and thence into the mold cavity. Air and gases within the mold cav ity jesca'pe through the vents as hereinbefore described. The metal rises from the bottom of the mold cavity upw'ard until engages withthe lowerend of the inserts v 14 when the casting is completed, having in the present case two inwardly extending oppositely I disposed tubular, bosses A,'.A, a heat dissi- Hating rib Bon the inner wall of the piston ead, two strengthening ribs. C, 0, between the side walls of the casting-and the bosses A,-'A, and an internal circumferentially ex tending flange D which serves to strengthen the lower part of the piston skirt and provide the, necessary thickness of wall for a wiping ring. The weight of the metal in the upper portion of the .gate serves to force thejnetal into the mold cavity to complete the castings, the upper end wall of the cast-' ing-being substantially in line with the, upp'f portion of; the gate which directly f s it. In addition to-the trapping out of air, this construction of gate serves to prevent oxidizing ofthe metals poured and other foreign materials from entering the mold cavity.

When the metal of the casting has set sufficiently the core pins 31 are removed by withdrawing them endwise. Next'the inside section 1'? of the main core is removed by withdrawing it axially or longitudinally upward. Then the outside metal core sections 17 and 17 are moved laterally inward, the necessary clearance being afforded by the upward movement, and preferably entire removal, of the section 17", and when they have cleared the internal flange D of the Next, by grasping casting, as shown in Fig. 7, they are drawn longitudinally upward and out of the mold.

of the quarter sections, said sections are swung laterally into the position indicated for one of said sections in Fig. 8. In this view the quarter section is clear of the pin boss but not of the circumferential flange D of the casting. However, by tipping the upper end of the section radially inward it is made to clear the flange D, whereupon it can be withdrawn longitudinally from the mold.

The first pair of quarter sections are thus withdrawn simultaneously, or nearly so, and thereupon the second pair can be freely swung laterally clear of the adjacent boss A of the casting and then withdrawn longitudinally from the mold.

After the removal of the core 17 the mold members 2 and .3 are unlocked and drawn apart far enough to permit the casting to be withdrawn, whereupon they are again moved into engagement with each other, locked and the operation repeated.

In Figs. 14 to 17 inclusive I have illustrated a modifiedform of construction. The base member 1 and the side members 2, 3 are substantially the same in construction as the corresponding parts of the mold described above and therefore need not be described in detail. In this second construction the core 40 is made up of three middle sections 40", F10 and 40 and four quarter sections 40 which are similar in many respects to the sections of the core 17 in the first form of construction. But the construction of the core 40 difiers in other re-. spects which I will now point out.

Instead of the circumferential recess f which in the first form of construction is disposed at a substantial distance from the open end of the piston casting and is designed to afford a form of wall providing for wiping ring grooves as well as to strengthen and stiffen the side walls of the piston at its open end, I form the core wlth a. circumferential depression f which is disposed at the extreme upper end of the mold cavity so as to form simply a strengthening and stiffening flange at the bottom of the side wall of the piston.

The quarter sections of each pair thereof have their adjacent faces recessed to form a pin boss cavity a but in this case the cavity passes entirely through the quarter sections, its inner wall being formed by a face of the core section 40*. In addition, com- .bined strengthening and heat dissipating ribs of modified for-m are employed, the quarter sections of the core being formed with adjacent recesses 12, b, and the lower end of the core section 40? with 0 which, together with the recesses 6', form the piston casting with two ribs joining the the handles 30 of one pair interlocking with recesses 0,

head, side walls and pin bosses as indicated in Fig. 14.,

With a rib construction such as last referred to, it is obvious that the rib recesses afford passage for 7 air and gases upward from the bottom of the mold cavity to the pin boss cavities and thence around the core pins 31 to the upper sides of the boss cavities. On the inner faces of the quarter sec-. tions of the cores I preferably form vent grooves 41, 41 leading from the pin boss recesses upward and outward to lines marking the corners of the adjacent core section 410 The corners of this section are slightly beveled from the pin boss cavities upward to the top of the core thus forming vent passages 42, 42 with which the grooves 4.1 communicate.

It will be understood that the several sections of the core 40 are provided with handles as in the case of the first form of construction and the mold is operated in substantially the same manner as set forth in connection with the first form of construcunderstood by those skilled in the permanent mold art.

It will be observed'that in my improved mold, while the main core is divided into a relatively large number of parts, the core structure when assembled in the mold is, nevertheless, very firmly and rigidly securedand exactly positioned. It will be seen that the row of middle core sections, preferably three in number, act, by virtue of their mutual engagement and their engagement and the walls of the mold body, to insure their own accurate disposal and firm support and at the same time accurately positlon and secure the quarter sections of the mold. Furthermore, these vitally important results are secured with core sections of such relative forms and dimensions that after the withdrawal of an inner section clearance is provided for the lateral movements of the outer sections sufficient to disengage the latter from all internal projections on the side walls of the casting, including not only the usual pin bosses but also internal roject-ions in planes transverse to the axis of the piston pin and even continuous circumferential internal pro ections such as have been illustrated hereln.

To those skilled in the art of castlng metals and their alloys, it will be apparent that my improved mold not only ossesses the advantages of the permanent molds used prior to my invention, such, for example, as the molds devised by Messrs. J. H. Bamberg and A. B. Norton, previously referred to, but is adapted for the production of cup shaped castings having internal projections of a complicated-character. And in particular my improvements make it ossible to cast in a permanent mold skirted pistons having internal strengthening or wlping ring flanges in the lower part of the piston walls as well as internal piston pin bosses and strengthening and heat dissipating ribs at or adjacent the head of the piston casting. Thus-I am enabled to cast skirted pistons for internal combustion engines in which the metal is disposed scientifically to secure adequate external bearing surface, and heat dissipating capacity as well as to securethe necessary strength with a minimum weight of metal.

It is to be understood that the construction of my improved mold can be varied widely Without departing from my invention, and that the specific forms of construction dis closed have been shown simply for the pur-.

poses of explanation and illustration.

' What I claim is:

1. In a permanent mold for piston castings, the combination with the permanent mold body having a cavity adapted to form the outer side wall of the'piston casting and having a gate through which molten metal may be introduced into the cavity, of a permanent sectional core supported on the mold body and extending into. its cavity to.

form the inner sidewall of the piston casting, the said core comprislng a ser es of more than two sections arranged in a row across the mold cavity with two of them engaging the inner side wall of the casting, and a third, interior section between the said two, and the core having also additional sections arranged on opposite sides of the said row of sections to engage the inner side wall of the casting, the said additional sections being exteriorly formed with cavities to form a pair of pin bosses on the inner side wall of the iston casting with their common axis at rlght angles to the said row of core sections and all of the exterior sections of the core being formed With alining depressions arranged to form an inwardly extending circum'ferential flange on the inner side wall of the piston casting, the several sections of the core being formed and arranged so that the said interior section when moved endwise afiords clearance to permit the outer sections a of the core to be successively moved laterally out of engagement with the internal projections of the piston casting and then endwise from said casting.

2. In a ermanent mold for skirted piston castings, the combination with 'a permanent mold body having a cavity open at one end and adapted to. form the outer head and side walls of the piston casting and having a gate through which molten metal can be introduced into the cavity, of a permanent sectional core supported on the mold body within a surrounding wall'thereof and extending into the cavity'of the mold to form the inner to form an inwardly extending circumferen- 1 tial flange on the inner side walls of the piston casting, the said core also having a series of more than two sections arranged in a row across the mold cavity with two of them engaging the inner side wall of the casting and the said core-supportingwall of the mold body at opposite points, one of the two having an interlocking engagement with the mold body and a third, interior section be tween said two, and the core having also sections arranged on opposite sides of said 3 row of sections to engage the inner side wall of the casting, the several sections belng (formed and arranged so that the said-inte rior section when moved endwise afi'ords clearance to permit the outer sections of the core to be successively moved laterally. outof engagement with the pin bosses and the inwardly extending flange of the piston cast ing and thenendwise out of sa1d castlng.

3. ,In a permanent mold for skirted pistoncastings, the combination with a permanent mold body having a cavityopen at' one end and adapted to form the outer head and side walls of the piston casting and having a I gate through which molten metal can be introduced into the cavity, of a permanent sectional core supported on the mold body within a surrounding wall thereof and] ex--- tending into the cavity of the mold to form the inner head and side walls of the piston casting, said core having its outer surface formed with cavities to form a-p'air of pin bosses on the inner side wall of, the piston cumferential flange on the inner side wall of the piston casting, the said core also having a series of three sections arranged in a row across the mold cavity with the two outside sections engaging the inner side wall of the casting and the said core-supporting wall of casting and with a circumferential depression arranged to form an inwardly extending 011 ment with said core supporting wall and with the third, interior section of said series, and the core having also sections arranged on opposite sides of said row of sections to, engage the inner side wall of the casting the several sections being formed and arranged so that the-said. interior section when withdrawn endwisejafi'ords clearanee to permit the outer sections ofthe core to be successively moved laterally out of engagement with the pin bosses and the inwardly extending flange of the piston cast- 7 ing and then endwise out of said casting.

4. In apermanent mold for skirted piston castings, the combination with a permanent I mold body having a cavity open at one end and adapted to form the outer'head and side walls of the piston casting and having a gate through which molten metal canibe in-' troduced into the cavity, of "a permanent sectional core supported on the moldbody within a surrounding wall thereof and ex tending into the cavity of the mold to form the inner head and side walls of the piston casting, the core comprising three middle sections arranged in a row across the mold cavity with the two outside sections engaging the inner side wall .of the casting and the said core supporting wall of the mold body at oppositepoints and comprising also two pairs'of quarter sections arranged re endwise to form a clearance permitting the lateral movement and endwise withdrawal first of the other middle sections and then of the quarter sections.

5. In a permanent mold for skirted piston castings, the combination with a permanent mold body having a cavity open at one end and adapted to form the outer head and side walls of the piston casting and having a gate through which molten metal can be introduced into the cavity, of a permanent sectional core supported on the mold body within a surrounding wall thereof and extending into the cavity of the mold to form the inner head and side walls of the piston casting, the core comprising three' middle sections arranged in a row across the mold cavity with the two outside sections engaging the inner side wall of the casting and the said core supporting wall of the mold body at opposite points and comprising also' two pairs of quarter sections arranged respectively on the opposite sides of the middle sections, the quarter sections'of each pair having their abutting faces recessed to form a cavity for one of the two pin bosses on the inner side wall of the piston casting and a strengthening rib or the like extending between said boss and the piston head, and the exterior sections of the core being formed with a circumferential depression to form an internal circumferential flange on the slde wall of the piston casting, the lnside 1 middle section of the casting being movable endwise to form a clearance permitting the lateral movement and endwise withdrawal first of the middle sections and then of the quarter sectlons.

the opposite sides of the, the quarter sections of each 6. In a permanent mold for skirted piston castings, the combination with a permanent mold body having a cavity open at one end and adaptedto form the outer head and side walls of the piston casting and having a gate through which molten metal can be in-- troduced into the cavity, of a permanent sectional core supported on the mold body and-extending into the cavity of the mold to form the inner head and side Walls of the piston casting, said core comprising a middle section adapted to be withdrawn endwise from the casting and two pairs of quarter sections arranged on opposite sides of the middle section, the quarter sections of each pair having their abutting faces recessed to form a cavity for one of the two internal pin bosses on the side wall of the piston casting and being formed also with venting grooves in their abutting faces leading from the head wall of the casting to the lower side of the pin bosscavity, and

the core sections having also venting outlets tending into the cavity of the mold to form the inner head and side walls of the piston casting, said core comprising a middle section adapted to be withdrawn endwise from the casting and two pairs of quarter sections arranged on opposite sides of the mid dle section, the quarter sections of the core having their mutually abutting faces recessed to form cavities for pin bosses on the inner side walls of the piston casting and an internal rib on the head of the piston casting, and, the quarter sections of each pair being formed with venting grooves in their mutually abutting faces leading from the rib cavity to the lower side of the adjacent pin boss cavity, and the core parts having venting outlets leading from the upper sides of the pin boss cavities to the exterior of the mold.

p 8. In a permanent mold for skirted piston castings, the combination with a permanentfmoldbody having-a cavity adapted to form theouter Walls of-the piston casting and having a gate through which molten metal may be introduced into the cavity, of a permanent core supported on the mold and extending into its cavity to form the inner walls of the piston'casting, the said core being divided longitudinally into seven parts six of which directly contact exteriorly with the inner side wall of the casting and interiorly with the seventh interiorly arranged section, certain of the six exterior sections of the core being exteriorly formed with cavities to form a pair of pin bosses on the inner wall of the piston casting and all of. the exterior sections of the core being formed with alining depressions arranged \to form an inwardly extending circumferential flange on the inner sidewall of the piston casting, the several sections of the core being formed and arranged so'that the in terior section when moved endwise affords clearance to permit the outer sections of the core to be successively moved laterally out of engagement with the internal projections of'the piston casting.

piston casting, said core having its outer surface formed with cavities toform a pair of pin bosses on the inner side wall of the piston casting and also a circumferential \GPI'BSSlOIl arranged to .form an inwardly extending circumferential flange on the inner side wall of the piston casting, the said core also comprising a series of more than two sections arranged in a row across the mold cavity with the two outside sections engaging the inner side wall of the casting and the said core supporting wall of the mold body at opposite points, the said row of core sections and the mold body being held in operative relation by means comprising an interlocking connection between one of the said outside sections and the core supporting wall of the mold body and by an interlocking" connection between said outside section and the adjacent interior section of the series, and the co-re'having, alsg, sectionsarranged on opposite sides of saldrow of sections to engage the inner sldewall of the casting, the several sections belng formed and arranged sothat the endwise movementof the interior section affords clearance. to permit the other sections of the core to be successively moved laterally out of engagement with the pin bosses and the inwardly extending flange of the piston casting and then endwise out of said casting.

In testimony whereof I afiix'my' signature.

FREDERIG A. PARKHUR'ST. 

